Numerous devices have been developed to address the recurring issue of maximizing the mechanical properties of a catheter or other medical access device to be advanced through a lumen. One such key property is generally referred to in the art as “pushability,” a term used to describe the rigidity of a device and its ability to advance through a lumen. See as an example U.S. Pat. No. 7,022,106. Another such property is the flexibility of a device. It is desirable for a device to be flexible enough to allow the device to traverse contorted and curved scopes and passages in the body. At the same time, the tip rigidity allows the device to better penetrate tissue, and the “pushability” allows proximal force transmission to the distal tip. Most composite materials provide for the flexibility needs, but do not meet the tip rigidity and pushability needs. Stainless steel provides very good rigidity and pushability, but is very limited in terms of flexibility.
Accordingly, companies have utilized various machining techniques in an attempt to impact these key properties. Current patents and technology have employed relief notches in both stylets and cannula tubing in an effort to increase flexibility. One example of such “static” flexibility is described in U.S. Patent Application Publication No. 2004/133124 to Bates, et al. Bates discloses a cannula and a stylet with notches designed to increase flexibility, but only in one plane of operation. However such notching does not allow for custom or adjustable flexibility and rigidity that is required in many medical procedures. As a result, such a device is flexible only in a fixed, constant or a “static” manner, and is thus of limited usefulness.
As one example of desired dynamic flexibility, it is necessary in certain procedures that the distal tip section initially be more flexible in order to accommodate tip deflection of a scope or introducer. As the device tip protrudes from the scope/introducer, it becomes more rigid, while at the same time the subsequent distal section is made more flexible to accommodate passage through the deflected scope/introducer. Under current art and designs, there is no method or device that will allow for this real-time modification and/or adaptation of flexibility. Such “tunable flexibility” features that are variable, adjustable and dynamic have broad application for endoscopic, bronchoscopic and laparoscopic procedures. Such technology could also be applied to intravascular, neurosurgery, optical procedures and a broad range of minimally invasive surgical procedures.
For instance, certain procedures require the device to navigate acute 135° angles during certain intralumenal operations. ERCP (endoscopic retrograde cholangiopancreatography) procedures require such convoluted paths and are becoming much more popular due to the improved patient outcomes derived through this technique. The procedure requires considerable flexibility, and considerable device length. However, with standard flexible materials, the longer the device is, the less “pushability” it will have at the tip of the device. Specifically, current technology makes use of conventional devices very difficult or impossible for ERCP. Current technologies are either too rigid to approach the desired target areas, or too flexible to effect any force transmission to the distal tip if they do achieve the target site. There are no known technologies that allow a material to be “tunable” with both good flexibility and good pushability within the desired portions of the same device, or flexible in the desired place of flexibility.
Current patented technologies describe only very simplistic relief notches that are in no way customized or engineered to allow variability in material performance, and provide only static flexibility. For instance, the medical device described in U.S. Pat. No. 6,419,641 may be too flaccid upon exiting the curved introducer to penetrate and obtain an adequate tissue core specimen in a “hardened” sclerotic liver. Conversely, the distal tip of said device may be too rigid to traverse a tighter than normal curve in the introducer as is required from time to time. In addition, the '641 patent is completely “static” in its operation, in that the flexibility designed into the device occurs only at one location, and in one plane. Thus, it actually teaches away from the dynamic flexibility enabled by the present teachings. Similarly, the device disclosed in U.S. Patent Application Publication No. 2004/133124 to Bates, et al. teaches away from the concept of “tunable” flexibility. The device described in Bates defines notches in the cannula and stylet that “face in the same direction” to allow flexibility in only one plane, namely “the plane perpendicular to the plane of the notch.” Thus, again, flexibility is not turnable, it is found only at a given device location and is solely in one place. The Roth device design manufactured by Cook exhibits some flexibility, but does not transfer cutting energy to the distal tip effectively enough to obtain adequate biopsy samples. Conventional fine needle aspiration devices also suffer from a similar lack of effectiveness in transferring force for penetrating the surface of the target area. Forceps designed for tissue removal and retrieval are also unable to penetrate beneath the surface of the target site in many instances.
Accordingly, there is a need among physicians for devices that can traverse contorted and curved introducers and endoscopes while maintaining the option of a maximum amount of tip rigidity and pushability in the distal and other segments of the device, as needed, and that is adaptable to numerous procedures, such as biopsies of the pancreas, bile duct, or of “hardened” or sclerotic liver. There is a further need for a technology that allows for such a device to exhibit custom tunability of flexibility at specific points along the length of the device.
One mechanism for manufacturing a stylet according to the teachings herein requires custom machining of certain notch sets into the length of the stylet at predetermined places. Although machined notches (including ground, laser, etc.) in stylets can achieve dynamic performance profiles, the machined notches can currently pose cost challenges for mass produced bi-lumenal devices. Accordingly, there is a need for suitable manufacturing methods to create inexpensive stylets that flex in separate fields as described herein.